decelerate vs slow up

decelerate and slow up both are verbs.

Word	Noun	Adjective	Verb	Adverb
decelerate	No	No	Yes	No
slow up	No	No	Yes	No

As verbs, decelerate and slow up are synonyms defined as:

Other synonyms of decelerate include retard, slow, slow down.

As verbs, slow up is a hyponym of decelerate; that is, slow up is a word with a more specific, narrower meaning than decelerate:

Other hyponyms of decelerate include slow, slow down, delay, detain, hold up.

decelerate (verb)	slow up (verb)
lose velocity; move more slowly	lose velocity; move more slowly
reduce the speed of	cause to proceed more slowly
	become slow or slower